1. Technical Field of the Invention
This invention relates generally to communication devices and more particularly to the communication devices that communicate in multiple frequency bands.
2. Description of Related Art
Wireless communication systems are known to support wireless communications between wireless communication devices affiliated with the system. Such wireless communication systems range from national and/or international cellular telephone systems to point-to-point in-home wireless networks. Each type of wireless communication system is constructed, and hence operates, in accordance with one or more standards. Such wireless communication standards include, but are not limited to IEEE 802.11, 802.15, 802.16, long term evolution (LTE), Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), wireless application protocols (WAP), local multi-point distribution services (LMDS), multi-channel multi-point distribution systems (MMDS), and/or variations thereof.
An IEEE 802.11 compliant wireless communication system includes a plurality of client devices (e.g., laptops, personal computers, personal digital assistants, etc., coupled to a station) that communicate over a wireless link with one or more access points. As is also generally understood in the art, many wireless communications systems employ a carrier-sense multiple access (CSMA) protocol that allows multiple communication devices to share the same radio spectrum. Before a wireless communication device transmits, it “listens” to the wireless link to determine if the spectrum is in use by another station to avoid a potential data collision. In other systems, transmissions can be scheduled using management frames or power save multi-poll (PSMP), for example. In many cases, the transmitting device (e.g., a client device or access point) transmits at a fixed power level regardless of the distance between the transmitting device and a targeted device (e.g., station or access point). Typically, the closer the transmitting device is to the targeted device, the less error there will be in the reception of the transmitted signal.
A cognitive radio is a wireless communication device that can adjust transmission or reception parameters to communicate efficiently to avoiding interference. This alteration of parameters can be based on the active monitoring of several factors in the external and internal radio environment, such as radio frequency spectrum, user behavior and network state.
When one or more of these communication devices is mobile, its transmit and receive characteristics can change with the motion of the device, as it moves closer or farther from a device it is communication with, and as the transmission environment changes due to the devices position with respect to reflecting members, interfering stations, noise sources, etc.
The limitations and disadvantages of conventional and traditional approaches will become apparent to one of ordinary skill in the art through comparison of such systems with the present invention.